314 



[March, 



Heights of Places determined by Lieut. HernpoNj JJ* S. N* 



A dotted hne on the diagram represents Lieut. Herndon's track above the 

 level of the sea, according to the above experiments. " By this track it will be 

 perceived," says Lieut. Maury, *'that after ascending the Andes, and coming 

 down the Amazon to a considerable distance, he ascended or went up hill. Now 

 we kr.ow that this was not the case, because he was all the time drifting down 

 the stream in a canoe. To reconcile this apparent paradox between the inclina- 

 tion of this slope of the continent, as shown on the one hand by the running 

 water of the rivers, and on the other by the pressure of the air, it is necessary 

 to suppose, that when he boiled his water at the eastern base of the Andes, he 

 was in fact under a bank of atmosphere, and that the pressure under this bank 

 was so great as to force the boiling point up very nearly to the sea level. 



" Let us now proceed to account as best we may, for this bank, or increased 

 atmospheric pressure. 



" These experiments were made in south latitude, and in the trade wind region 

 of that hemisphere. These winds strike nearly perpendicularly against the 

 Andes, the tops of which range extend in many places nearly, if not quite as 

 high, as do the trade winds themselves. Now, then, what is the effect of such 

 an obstruction as the Andes afl^ord to the passage of the southeast trade winds 1 

 If we may judge by the effect of similar obstructions to running water, we have 

 no hesitation in saying that the effect is to bank up. 



"Pot Rock and other obstructions to the rapid current of Hurlgate taking 

 small things to represent great may serve us with an illustration that will 

 assist me in making myself clear. Any one who witnessed the water running 

 over that rock, could not fail to be struck with the fact, and the extent to which 

 the water was piled up, not over the rock, but up stream from it j not only was 



